Synergistic additive combination for antistall gasoline



ite States atet 1 3,014,792 SYNERGISTIC ADDITWE COMBINATION FORANTISTALL GASGLINE Julius Capowski and William L. Wascher, Jr., Pitman,N.J., assignors to Socony Mobil Oil Company, Inc., a corporation or NewYork No Drawing. Filed Sept. 1), 1960, Ser. No. 56,651 3 Claims. (Cl.44-63) This invention relates to gasoline compositions adapted toimprove the operation of internal combustion engines. It is moreparticularly concerned with motor fuels that provide improved engineoperation under cool, humid weather conditions.

As is well known to those skilled in the art, frequent stalling ofautomobile engines, especially during the Warmup period, has been acommon occurrence. This difficulty is most pronounced in postwar carshaving automatic transmissions and a consequent limit on the maximumpermissible idle speed, although icing also occurs in cars withoutautomatic transmissions. Stalling of this type, of course, is a definitesafety hazard, as well as a decided inconvenience in frequent restartingof the engine.

It is now recognized that stalling during the warm-up period isattributable to the formation of ice on the throttle plate and thecarburetor barrel near it. The water which forms the ice does not comefrom the gasoline, i.e. as enuained water, but from the air that entersthe carburetor. As has been mentioned hereinbefore, stalling generallyoccurs in cool, humid weather, when the temperatures are above about 30F. and below about 60 F. and the relative humidity is about 65 percentand higher, up to 100 percent. The most critical conditions aretemperatures of 35-45 F. and 100 percent relative humidity.

As the gasoline evaporates in the carburetor, it reduces the temperatureof the surrounding metal by as much as 50 F. Moisture in the incomingair comes in contact with these parts and begins to build up ice on thethrottle plate and in the carburetor barrel. The more moist this air is,the greater the build-up of ice. Then, when the engine is idled, thethrottle plate closes and the ice chokes off the normal small flow ofair through the small clearance between the throttle plate and thecarburetor wall. This causes the engine to stall. The engine can usuallybe re-started when the heat from the exhaust manifold melts the icesufficiently. However, stalling will continue until the engine iscompletely warmed up.

I Carburetor icing occurs in many vehicles when cruising at speeds of3060 m.p.h. Such icing is apronounced problem in the case of certaintrucks and in cars equipped with carburetors having Venturi-typefuel-airmixing tubes (emulsion tubes). Such carburetors are found in manyEuropean cars. The ice builds up on the tube and restricts the flow ofair, thereby enriching the fuel mixture and reducing efiiciency.Eventually the engine may stall.

Gasoline is a mixture of hydrocarbons having an initial boiling pointfalling between about 75 F. and about 135 F. and an end-boiling pointfalling between about 250 F. and about 450 F. The boiling range of thegasoline, of course, reflects on its volatility. Thus, a higher boilinggasoline will be less volatile and give less stalling difficulty. It hasbeen proposed in the art that a gasoline having an ASTM mid-boiling(50%) point of 310 F. or higher will not be subject to stalling.Although this may be the case for a given series of gasolines, however,it is not the sole and controlling factor. Gasolines of highermid-boiling point but a low initial boiling point (e.g. full boilingrange gasolines) can induce stalling when the aforementionedstall-inducing atmospheric conditions are prevalent. Thus, any gasolinewill give difficulty in damp, cool weather. In modern engine operation,however,

phoric acid.

- of synergistic combination of a tetrahydropyrimidine havice control ofstalling by means of volatility is not feasible, because otherperformance characteristics are afiected.

It has now been found that stalling during engine warmup can be overcomesimply and economically. It has been discovered that small amounts of asynergistic combination of certain substituted tetrahydropyrimidines andcertain amine salts of partial alkyl esters of orthophosphoric acid,when added to motor gasoline, will overcome stalling difficultiesattributable to carburetor icing.

Accordingly, it is an object of this invention to provide an improvedmotor fuel. Another object is to provide a motor fuel adapted to preventstalling during engine warm up in cool, humid weather. A specific objectis to provide an antistall gasoline containing a synergistic combinationof certain substituted tetrahydropyrimidines and certain amine salts ofpartial alkyl esters of orthophos- Other objects and advantages of thisinvention will become apparent to those skilled in the art, from thefollowing detailed description.

In general, this invention provides a motor gasoline containing a smallamount, sufiicient to inhibit stalling,

ing the structure:

wherein R is naphthenyl and R is an aliphatic hydrocarbon radical having8 to 18 carbon atoms, and an amine phosphate having the structure:

wherein R is an aliphatic hydrocarbon radical of 6 to 18 carbon atoms, Ris an alkyl radical having 6 to 18 carbon atoms, and R" is hydrogen orR'. p

The tetrahydropyrimidines that form part of the synergistic combinationof this invention have been proposed as carburetor detergents incopending application Serial Number 757,457, filed August 27, 1958, andnow Patent No. 2,961,308. Although efiective carburetor detergents, thetetrahydropyrimidines, at the concentrations used, have littleeffectiveness by themselves as antistallingadditives. Thetetrahydropyrimidines contemplated herein have the structure:

/CH2 CH2 CH2 N NR 1y utilizable herein are naphthenic acids containingbetween about 10 and about 30 carbon'atoms. Such acids can have an acidnumber (mg. KOH per gram) varying between about and about 220,corresponding to an average molecular weight of between about 420- andabout 275. A particularly useful naphthenic acid, Acid X, has.

an average molecular formula, C H an average moiecular weight of 297; anacid number of 178; about 5 percent unsaponifiables; and distils, at apressure of 2 mm. Hg, over the range 315 185 F.

The diamine reactant used to make the additives contemplated herein isN-aliphatic hydrocarbon substituted propylene diarnine having theformula,

wherein R is an aliphatic hydrocarbon group containing between about 8carbon atoms and about 18 carbon atoms. The diamine reactant can be apure compound, but, in practice, it will often be a mixture of purediamines. Several mixtures of diamine reactants are available on acommercial scale. Amine A is mixture of N-substituted propylene diaminesof the formula set forth hereiubefore, wherein about 20 percent of the Rgroups are hexadecyl, about 17 percent are octadecyl, about 26 percentare octadecenyl, and about 37 percent are octadecadienyl. Amine B is asimilar mixture wherein 8 percent of the R groups are octyl, about 9percent are decyl, about 47 percent are dodecyl, about 18 percent aretetradecyl, about 8 percent are hexadecyl, about 5 percent areoctadecyl, and about 5 percent are octadecenyl. In another mixture,Amine C, about 2 percent of the R groups are tetradecyl, about 24percent are hexadecyl, about 28 percent are octadecyl, and about 46percent are oetadecenyl. Amine C is particularly preferred.

The tetrahydropyrimidines utilizable herein are condensation products ofthe naphthenic acid and the propylene diamine reacted in a 1:1 molarratio. As water is a by-product of the reaction, provision is made forwater removal. Thus, as is well known, temperatures of 130 275 C. can beused for periods of time until evolution of water ceases, usually 4-l6hours. Other means of facilitating water removal can be employed, suchas, for example, azeotropic distillation and operation undersubatmospheric pressure.

The amine salt components of the synergistic combination of thisinvention are salts of mono and/ or di-esters of orthophosphoric acidhaving the structure:

RI! wherein R is an aliphatic hydrocarbon radical having between about 6carbon atoms and about 18 carbon atoms, R is an alkyl radical havingbetween about 6 carbon atoms and about 18 carbon atoms, and R" ishydrogen or R.

The phosphate ester portion of the amine phosphate component is amono-ester of orthoiphosphoric acid, a

di-ester of orthorphosphoric, or a mixture of mono-ester and di-ester.The ester groups of the phosphate ester are alkyl radicals havingbetween about 6 and about 18 carbon atoms, preferably between about'6and about 10 carbon atoms. The monoand/or di-esters are suitablyprepared by reacting an alcohol with phosphorus pentoxide in molarproportions of alcohol to phosphorus pentoxide varying between 2 and 4.The esterification reaction is generally carried out at temperaturesfrom 60 to-212 F. with active stirring for a time needed to complete thereaction as evidenced by complete solution of: the phosphorus pentoxide.An especially preferred phosphate ester amine salt is the octylaminesalt of a mixture of monoand di-octyl phosphate.

The components of the synergistic additive combinations are each used inthe gasoline at concentrations varying betweenv about 0.001 percent andabout 0.03 percent, by weight ofthe gasoline. ester amine salt totetrahydropyrimidine will vary between about 5:1 and about 1:1,respectively. Preferably, the weight ratio of ester salt totetrahydropyrimidine will be about 3:1, respectively.

The antistall additives of the invention may be used in the gasolinealong with other antistall addition agents or other additives designedto impart other improved properties thereto. Thus, antiknock agents,preignition inhibitors, anti-rust agents, metal-deactivators, dyes,antioxidants, etc., may be present in the gasoline. Also, the gasolinemay contain a small amount, from about 0.01 percent to about onepercent, by weight, of a solvent oil or upperlube. Suitable oils, forexample, include coastal and mid-continent distillate oils havingviscosities within the range of from about to about 500 S.U.S. at 100 F.Synthetic oils, such as di-ester oils, polyalkylene glycols, silicones,phosphate esters, polypropylenes, polybutylenes, and the iike, may alsobe used.

The following examples are for the purpose of illustrating thisinvention and demonstrating the effectiveness thereof. This invention isnot to be limited to the specific composition set forth in the examplesor to the operations and manipulations involved. Other materials andformulations as described hereinbefore can be used, as those skilled inthe art will readily understand.

The ability of an additive to inhibit stalling is demonstrated in thefollowing test:

HILLMAN-MINX ENGINE TEST' A standard Hillrnan-Minx engine, equipped witha Crosley single downdraft carburetor, was used in this. test. Athermocouple was attached to the throttle body to record the throttlebody temperature. An eight inch long Water-cooled standpipe was placedbetween the carburetor and manifold to prevent heat conduction. A spraychamber and an ice tower were used to saturate the incoming air withmoisture and to cool the air to about 40 F. before it entered thecarburetor.

In conducting a test, the engine was first run for about 10 minutes at2750 rpm. to bring the engine temperature to equilibrium. The engine wasthen shut ofi. When the throttle body temperature rose to 40 F., theengine was restarted with the idle speed set at 450 r.p.m.. so that thebase fuel stalled at idle in 10 seconds or less after at run-time of 50to 70 seconds. Run-time means the time that the engine was run at 2750r.p.m. before returning to idle.

All the runs were started when the throttle bodyreached 40 F. At theinstant of starting, the throttle arm was moved to the 2750 r.p.m.position and. a stop watch started. At the end of the selected run-time,the throttle arm was moved to the idle position. The time required tostall was recorded. Several tests were made for each fuel and therun-times were averaged.

The weight ratio of phosphate In evaluatingan additive, the base fuelwas first tested followed by the base fuel containing severalconcentrations of the additive. The system was flushed between testswith a solvent mixture of acetone, methanol, benzene and the fuel to berun next. Any improvement caused by the additive was reflected in alonger runtime (as compared to the base fuel) to cause stalling in 10-Seconds or less when the engine was idled. The more effective theadditive, the longer the run-time. 'The base gasoline used to evaluatethe antistall additives was a blend, by volume, of 78 percent platinumreformate gasoline, 16 percent natural gasoline, and 6 percent butane,having an API. gravity of 58.1. It had an ASTM boiling range of 78 F. to396 F., with a. mid-boiling point of 200 F.

Example 1 A mixture of 400 parts of naphthenic acid X and 510 parts ofAmine C was refluxed in'xylene solution for 8 hours. The reactionmixture was slowly heated to 265 C. and held at thattemperature untilthe evolution of;

water had ceased. Thirty-six parts (2 moles) water were" obtained. Thexylene solvent was removed, leaving a substituted tetrahydropyrimidinehaving a formula:

wherein R' is naphthenyl and R is 2 percent tetradecyl, 24 percenthexadecyl, 28 percent octadecyl, and 46 percent octadecenyl. The basegasoline and a blend of the additive of this example in the basegasoline were each subjected to the Hillrnan-Minx engine test. Pertinentdata are set forth in Table 1.

Example 2 There was obtained a commercially available phosphate esteramine salt, the octylamine salt of mixed monoand di-octyl phosphate,having the composition- Constituent: Wt. percent Carbon 59.14 Hydrogen 11.5 8 Phosphorus 8.06 Nitrogen 3.62 Oxygen 17.60

This material was blended in the base gasoline and the blend wassubjected to the Hillman-Minx engine test. Pertinent data are set forthin Table I.

Example 3 A blend in the base gasoline of the additive of Example 2 andthat of Example 1, in a weight ratio of 3:1, respectively, was subjectedto the Hillman-Minx engine test. Pertinent data are set forth in TableI.

1 Pounds per thousand barrels of gasoline.

It will be noted that the tetrahydropyrimidine (Example 1) was not aneifective antistall additive. The amine salt of phosphate ester (Example2) was somewhat effective. However, the combination of the two additives(Example 3) had a synergistic effect and gave results considerably morethan mere additive eflect of the two addition agents.

Although the present invention has been described with preferredembodiments it is to be understood that modifications and variations maybe resorted to, without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchvariations and modifications are considered to be within the purview andscope of the appended claims.

What is claimed is:

1. A motor gasoline containing between about 0.001 percent and about0.03 percent, by weight of the gasoline, of a synergistic combination ofa tetrahydropyrimidine having the structure:

CH2 CH2 wherein R is naphthenyl and R is an aliphatic hydrocarbonradical having between about 8 and about 18 carbon atoms, and an aminephosphate having the structure i i RII }II H R!!! wherein R" is analiphatic hydrocarbon radical having between about 6 and about 18 carbonatoms, R' is an alkyl radical having between about 6 and about 18 carbonatoms, and R is selected from the group consisting of hydrogen and R;the weight ratio of said amine phosphate to said tetrahydropyrimidine insaid synergistic combination being between about 5:1 and about 1:1.

2. A motor gasoline containing between about 0.001 percent and about0.03 percent, by Weight of the gasoline, of a synergistic combination ofa tetrahydropyrimidine having the structure:

wherein R is naphthenyl and R is an aliphatic hydrocarbon radical havingbetween about 8 and about 18 carbon atoms, and the octylamine salt of amixture of monoand di-octyl phosphate; the weight ratio of saidoctylamine salt to said tetrahydropyrimidine in said synergisticcombination being between about 5:1 and about 1:1.

3.A motor gasoline containing between about 0.001 percent and about 0.03percent, by weight of the gasoline, of a synergistic combination of atetrahydropyrimidine having the structure:

wherein R is naphthenyl and R is a mixture of aliphatic radicals ofwhich 2 percent are tetradecyl, about 24 percent are hexadecyl, about 28percent are octadecyl, and about 46 percent are octadecenyl, and theoctylamine salt of a mixture of monoand di-octyl phosphate; the weightratio of said octylamine salt to said tetrahydropyrimidine in saidsynergistic combination being between about 5:1 and about 1:1.

References Cited in the file of this patent UNITED STATES PATENTS2,863,742 Cantrell et a1. Dec. 9, 1958 2,863,904 Cantrell et a1. Dec. 9,1958 2,915,528 Raifsnider Dec. 1, 1959 2,919,684 Carrv Jan. 5, 19602,961,308 Andress Nov. 22, 19 60

1. A MOTOR GASOLINE CONTAINING BETWEEN ABOUT 0.001 PERCENT AND ABOUT0.03 PERCENT, BY WEIGHT OF THE GASOLINE, OF A SYNERGISTIC COMBINATION OFA TETRAHYDROPYRIMIDINE HAVING THE STRUCTURE: